Piezoelectric/electrostrictive device

ABSTRACT

A piezoelectric/electrostrictive device including a substrate and a connection plate having a first end joined to the substrate and an opposed second end extending along a first direction, and first and second opposed sides along a second direction perpendicular to the first direction. A fixing plate is joined to the second end of the connection plate. A first side of a first diaphragm is joined to the first side of the connection plate and an opposed second side of the first diaphragm is joined to the substrate. A first side of a second diaphragm is joined to the substrate and an opposed second side of the second diaphragm is joined to the second side of the connection plate. A piezoelectric/electrostrictive element is provided on at least a portion of at least one planar surface of at least one of the diaphragms.

TECHNICAL FIELD

The present invention relates to a device using apiezoelectric/electrostrictive film, particularly to the structure of apiezoelectric/electrostrictive device for improving the operationalcharacteristic of an element for converting electrical energy intomechanical energy such as mechanical displacement, mechanical force, orvibration and etc., and vice versa. Specifically, the present inventionrelates to a piezoelectric/electrostrictive device to be applied totransducers, various actuators, frequency-region functional components(filters), transformers, vibrators and resonators for communication andmotive power, oscillators, discriminators, and various sensors includingultrasonic sensors, acceleration sensors, angular velocity sensors,impact sensors, and mass sensors, and moreover unimorph- andbimorph-type elements used for servo shift elements described in “FromFoundation Up To Application of Piezoelectric/Electrostrictive Actuator”written by Kenji Uchino {edited by Japan Industrial Technical Center andpublished by MORIKITA SHUPPAN (transliterated)}, and to be preferablyadopted to various actuators used for mechanisms for shift andpositioning adjustment and angle adjustment of various precisioncomponents and etc. of optical equipment, precision equipment, etc.

BACKGROUND ART

Recently, a shift control element for adjusting an optical-path lengthor position on the sub-micron order has been requested in the opticaland magnetic recording fields, as well as the precision-machining field.To respond to this request, piezoelectric/electrostrictive actuatorshave been developed, which are elements using a displacement based onthe reverse or converse piezoelectric effect or electrostrictive effectcaused by applying an electric field to a piezoelectric/electrostrictivematerial such as a ferroelectric.

In the field of magnetic recording on a hard disc drive, storagecapacity has been remarkably increased in recent years. This is becausean attempt has been made to use a recording medium more efficiently byincreasing the number of recording tracks to increase the recordingdensity. Recording methods have also improved.

This attempt has been mainly made so far in the area of the voice coilmotor. Moreover, as a new technical art, an electrostatic-typemicroactuator micromachined in Si or Ni and used as the tracking systemof a magnetic head for a hard-disk drive has been attempted, asdescribed on pp. 1081-1084 in the preliminary manuscript collection of“1997 International Conference on solid-state Sensors and Actuators” of“TRANSDUCER'97”.

Moreover, Japanese Patent Application Laid-Open No. 10-136665 disclosesa piezoelectric actuator as shown in FIG. 24 in which a fixed portion103, a movable portion 104, and at least one beam portion 102 forconnecting the portions 103 and 104 to each other are integrally formedby forming at least one hole on a flat body made of apiezoelectric/electrostrictive material, and a strain generation portionis constituted by forming an electrode layer 105 on at least a part ofat least one beam portion 102 so that an expansion or a contractionmotion occurs in the direction connecting the fixed portion 103 with themovable portion 104, and a displacement mode of the movable portion 104to the fixed portion 103 generated due to the expansion or contractionmotion of the strain generation portion is an arc-shaped or rotationalmode in the plane of the flat body.

However, in the case of the conventional art for positioning a recordinghead mainly using a voice coil motor, it is difficult to accuratelyposition a recording head so as to accurately trace tracks when thenumber of tracks increases in order to correspond to a further increasein capacity.

The above-described technical art using an electrostatic-typemicroactuator obtains a displacement by applying a voltage between aplurality of flat electrodes formed through micromachining. However, itis difficult to increase a resonance frequency because of the structure.Consequently, the technical art includes such problems that vibrationsare not easily attenuated when a high-speed operation is performed.Moreover, there is a feature that the technical art isdisplacement-theoretically inferior in the linearity of thevoltage-displacement characteristic. Therefore, there are many problemsto be solved from the viewpoint of accurate alignment. Furthermore, theprocess of micromachining itself has a problem from the viewpoint of themanufacturing cost.

Furthermore, in the case of a piezoelectric actuator disclosed inJapanese Patent Application Laid-Open No. 10-136665, thepiezoelectric-operation portion has a monomorph structure. Therefore,the main-strain axis of a piezoelectric material becomes coaxial orparallel with the main-shift axis of the piezoelectric-operationportion. Thus, there are problems that the piezoelectric-operationportion itself generates only a small shift and the movable portion alsoshows a small displacement. Moreover, the piezoelectric actuator itselfis heavy and subject to harmful vibrations for operation such asresidual vibrations and vibrational noises under a high-speed operationas described in Japanese Patent Application Laid-Open No. 10-136665 andtherefore, it is necessary to suppress harmful vibrations by injecting afiller into a hole. However, the use of such a filler may adverselyinfluence displacement of the movable portion. Moreover, because it isunavoidable to constitute a piezoelectric actuator with apiezoelectric/electrostrictive material inferior in mechanical strength,there is a problem that the actuator is subject to materialstrength-imposed restrictions on shape and purpose.

SUMMARY OF THE INVENTION

The present invention is made to solve the problems of the abovepiezoelectric/electrostrictive device. According to the presentinvention, the following first to sixth piezoelectric/electrostrictivedevices capable of accurately performing in-plane movements andoperations at a high speed are provided.

That is, a piezoelectric/electrostrictive device in which apiezoelectric element is formed on at least a portion of at least oneplane of a diaphragm whose one side is joined to a substrate and atleast one side of one thin-walled fixing plate is joined to one side ofthe diaphragm so that the plane of the fixing plate and the plane of thediaphragm are perpendicularly intersected with each other, is providedas the first piezoelectric/electrostrictive device.

It is preferable that the first piezoelectric/electrostrictive deviceoperates in accordance with at least either of a θ-mode displacement inwhich a fixing plate is displaced like a pendulum in the directionvertical to a side of the fixing plate and vertical to the vertical axisabout the vertical axis vertically passing through the center of a fixedplane by using the joining face between the fixing plate and a diaphragmas the fixed plane and a φ-mode displacement in which a swing in thedirection vertical to a side of the fixing plate and vertical to thevertical axis is displaced like a pendulum while being followed by aswing in the direction parallel with a side of the fixing plate, thatis, the first piezoelectric/electrostrictive device drives the fixingplate by a piezoelectric element or detects the displacement amount ofthe fixing plate.

Moreover, a piezoelectric/electrostrictive device in which a fixingplate and a connection plate are joined with each other at their sides,and a diaphragm in which piezoelectric elements are arranged on at leasta portion of at least one plane is joined to the connection plate attheir sides in the direction perpendicular to the joining directionbetween the fixing plate and the connection plate, and at least parts ofsides of the connection plate and the diaphragm are joined to asubstrate, is provided as the second piezoelectric/electrostrictivedevice.

In this case, a part of a side of the connection plate to be joined tothe substrate represents a side opposite to the connection face of theconnection plate with the diaphragm. Therefore, the fixing plate and thesubstrate are connected with each other through the connection plate. Apart of a side of the diaphragm to be joined to the substrate representsa side opposite to the connection face of the diaphragm to theconnection plate or a side opposite to the connection face of thediaphragm to the fixing plate when the diaphragm is directly joined tothe fixing plate. Moreover, the joining configuration between theconnection plate or diaphragm and the substrate is common topiezoelectric/electrostrictive devices of the present invention to bedescribed later.

Furthermore, a piezoelectric/electrostrictive device in which a fixingplate and a connection plate are joined with each other at their sides,and two diaphragms are joined at their sides so as to hold theconnection plate in the direction perpendicular to the joiningdirection. between the fixing plate and the connection plate,piezoelectric elements are arranged on at least a portion of at leastone plane of at least one diaphragm, and at least parts of sides of theconnection plate and each diaphragm are connected with a substrate isprovided as the third piezoelectric/electrostrictive device.

In case of the third piezoelectric/electrostrictive device, it ispreferable to arrange piezoelectric elements on at least one plane ofone diaphragm and one or preferably, a plurality of slits on the otherdiaphragm. Moreover, in case of the second and thirdpiezoelectric/electrostrictive devices, it is preferable to join otherdiaphragm plates in which piezoelectric elements are arranged at one endof a fixing plate at their sides and alternately join a necessary numberof other connection plates and/or fixing plates and other diaphragms tothe above other diaphragms at their sides to increase a displacementamount.

Then, a piezoelectric/electrostrictive device in which a connectionplate and a diaphragm in which piezoelectric elements are arranged on atleast a portion of at least one plane are not connected with each otherbut connected with a fixing plate at their sides in parallel and atleast parts of the sides of the connection plate and the diaphragm arejoined to a substrate is provided as the fourthpiezoelectric/electrostrictive device.

Moreover, a piezoelectric/electrostrictive device in which a fixingplate joined to and held by two connection plates at sides is setbetween lateral sides of a concave portion formed on a substrate so asto be set between the lateral sides, two diaphragms are respectively setbetween each of the connection plates and the bottom sides of concaveportion in the direction perpendicular to the direction for theconnection plates to hold the fixing plate, and piezoelectric elementsare arranged on at least a portion of at least one plane of at least onediaphragm is provided as the fifth piezoelectric/electrostrictivedevice. In this case, the concave portion represents a portioncomprising facing sides and a bottom side for connecting these sides. Incase of the present invention, it is not always necessary that a bottomside is a plane. It is possible to change the bottom side to variousshapes by forming a recess or a protrusion on the bottom side as long asit does not influence the displacement of a fixing plate or measurementof a displacement amount.

Moreover, a piezoelectric/electrostrictive device in which a fixingplate is joined to and held by two connection plates at sides is set ona through-hole formed in a substrate, at least a plurality of diaphragmsis bridged between each of the connection plate and the through-hole orbetween the fixing plate and the through-hole so as to span them in thedirection perpendicular to the direction for the connection plates tohold the fixing plate, and piezoelectric elements are arranged on atleast a portion of at least one plane of at least one of the diaphragmis provided as the sixth piezoelectric/electrostrictive device.

In case of the sixth piezoelectric/electrostrictive device, it ispreferable to arrange piezoelectric elements on at least one plane ofone diaphragm among pairs of diaphragms facing each other through eachconnection plate or a fixing plate and to form one or preferably, aplurality of slits on the other diaphragm.

In case of the second to sixth piezoelectric/electrostrictive devices,it is preferable to form a slit or constricted portion (narrow portion)on a connection plate because a displacement amount can be increased.Moreover, it is preferable to use a structure in which a diaphragm isfitted to and joined to a concave portion formed by a connection plateand a substrate. To obtain the above structure, it is preferable tointegrally form a fixing plate, connection plate, and diaphragm from onediaphragm plate and form a substrate integrally with a diaphragm plateand a base plate by superimposing the diaphragm plate on the base plate.The concave portion represents a concave portion in which a substrateitself is formed into a concave shape, a concave portion in which acutout is formed on a part of the outer periphery of a substrate, or aconcave portion when regarding a part of a through-hole formed on asubstrate as a concave portion.

Moreover, it is preferable to bond a spring plate with at least oneplane of a connection plate and join the spring plate to a substrate ora spring-plate reinforcement portion. In this case, it is preferablethat the spring plate is not bonded by using an adhesive or the like butthe spring plate is formed integrally with an intermediate plate fittedbetween and integrated with a diaphragm plate and a base plate or formedintegrally with a spring-plate reinforcement portion formed integrallywith the diaphragm plate and also formed integrally with a connectionplate. In case of the spring plate, when there are two or moreconnection plates, it is preferable that shapes formed by bondingconnection plates with the spring plate become the same. Moreover,though the shape of the spring plate is not restricted, it is preferableto use a simple shape such as a pillar-shape or plate shape or a shapeto be easily formed such as a U-shaped, H-shaped, or quadrangular framebecause the manufacturing process can be simplified. Furthermore, it ispreferable to use a reinforcement plate to be bonded with a spring plateand joined to a side of a substrate. In this case, it is preferable toform the reinforcement plate integrally with the spring plate and thesubstrate.

These second to sixth piezoelectric/electrostrictive devicesrespectively have a structure preferable to use either of a θ-modedisplacement in which a fixing plate displaces like a pendulum in thedirection vertical to a side of the fixing plate and vertical to thevertical axis vertically passing through the center of a fixed planeabout the vertical axis by using the joining face between a connectionplate and a substrate as the fixed plane and a φ-mode displacement inwhich a swing in the direction vertical to a side of the diaphragm andvertical to the vertical axis displaces like a pendulum while beingfollowed by a swing in the direction parallel with a side of the fixingplate.

Moreover, in case of every piezoelectric/electrostrictive devicedescribed above, it is preferable to form a diaphragm and/or aconnection plate by joining the diaphragm and/or connection plate to aside of an optional-shaped through-hole formed in a substrate becausethe piezoelectric/electrostrictive device can be easily handled and itsdamage can be avoided. Furthermore, it is preferable to divide onepiezoelectric element into two parts and use one of them as a drivingelement and the other of them as an auxiliary element because it ispossible to improve the positioning accuracy. In this case, theauxiliary element represents a trouble-shooting element, displacementconfirming/deciding element, or auxiliary driving element. Furthermore,it is preferable to arrange piezoelectric elements on at least twoplaces and use the piezoelectric element on at least one place as adriving element and the piezoelectric element on at least the otherplace as an auxiliary element because the driving accuracy andpositioning accuracy are improved. Therefore, it is also possible tofurther divide each of piezoelectric elements arranged on two places ormore into two parts.

Furthermore, it is preferable to cover each piezoelectric element, theelectrode of the piezoelectric element, and an electrode lead to beconnected to the electrode with an insulating coating layer made ofresin or glass. Thus, even under a state in which apiezoelectric-element portion is soaked in a liquid, the electrode isnot short-circuited and it is possible to use thepiezoelectric/electrostrictive device. In this case, to improve theperformance of the piezoelectric/electrostrictive device, it ispreferable to use resin as an insulating coating material instead ofglass, fluorocarbon resin superior in chemical stability is mostpreferably used, and it is also possible to preferably use silicon resinthough this is inferior to fluorocarbon resin in chemical stability.When forming the above insulating coating layer, it is preferable tofurther form a shielding layer made of conductive materials on thesurface of the insulating coating layer to minimize the influence ofexternal noises such as electromagnetic waves.

It is preferable that substrate, fixing plate, connection plate,diaphragm, spring plate, spring-plate reinforcement portion, andreinforcement plate constituting a piezoelectric/electrostrictive deviceof the present invention are integrally formed by using a stabilized orpartially-stabilized zirconia. A material mainly containing a componentmade of lead zirconate, lead titanate, and lead magnesium niobate ispreferably used as the piezoelectric film of the piezoelectric element.Moreover, by trimming and adjusting the shape of a fixing plate, springplate, or connection plate through laser-beam processing or cutting, itis possible to obtain a preferable shape each time depending on the typeof an actuator to be applied. Furthermore, it is possible to easilyadjust the displacement amount of a fixing plate. Furthermore, it ispreferable to adjust the effective electrode area of the piezoelectricelement by laser-beam-processing or cutting the electrode of apiezoelectric element, because a piezoelectric characteristic suitablefor a use or a necessary spec can be easily obtained.

As the result of comparing a piezoelectric/electrostrictive device ofthe present invention with the piezoelectric actuator disclosed inJapanese Patent Application Laid-Open No. 10-136665, because thepiezoelectric/electrostrictive device of the present invention has aunimorph- or bimorph-type structure having a diaphragm and thereby, thedirection of the main-strain axis of a piezoelectric material isdifferent from that of the main-displacement axis of a piezoelectricoperating portion (portion causing a displacement by the strain of thepiezoelectric material), it is found that thepiezoelectric/electrostrictive device of the present invention hasadvantages that the strain of the piezoelectric material can be enlargedto the bending mode by effectively using the above feature andtherefore, a large displacement of a fixing plate can be obtained.Moreover, a piezoelectric/electrostrictive device of the presentinvention allows functional differentiation and its substrate and thelike other than its piezoelectric material can be constituted with amaterial mainly containing zirconia superior in mechanical strength andtoughness. Therefore, there is an advantage that a compact, thin, andlightweight device having a desired strength can be obtained.Furthermore, a piezoelectric/electrostrictive device of the presentinvention has features that the displacing characteristic is not easilyinfluenced from the outside and therefore, it is unnecessary to use afiller or the like.

The expression “piezoelectric” of piezoelectric element, piezoelectricfilm, and piezoelectric ceramics used for the present invention includesthe meanings of both “piezoelectric” and “electrostrictive.”

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1(a) to 1(d) show perspective views of an embodiment of apiezoelectric/electrostrictive device of the present invention, in whichthe arrangement of and the number of fixing plates are changed;

FIG. 2 shows a perspective view of an embodiment of a piezoelectricelement to be used for a piezoelectric/electrostrictive device of thepresent invention;

FIG. 3 shows a perspective view of another embodiment of a piezoeltricelement to be used for a piezoelectric/electrostrictive device of thepresent invention;

FIG. 4 shows a perspective view of still another embodiment of apiezoelectric element to be used for a piezoelectric/electrostrictivedevice of the present invention;

FIGS. 5(a) to 5(c) show another embodiment of apiezoelectric/electrostrictive device of the present invention, in whichFIG. 5(a) is a top view of the embodiment, FIG. 5(b) is an illustrationof the θ mode, and FIG. 5(c) is an illustration of the φ mode;

FIGS. 6(a)-(d) show top views showing still another embodiment of apiezoelectric/electrostrictive device of the present invention;

FIGS. 7(a) to 7(e) show still another embodiment of apiezoelectric/electrostrictive device of the present invention, in whichFIG. 7(a) is a top view of the embodiment and FIGS. 7(b) to 7(e) aresectional views of the embodiment;

FIGS. 8(a)-(b) show illustrations related to driving of apiezoelectric/electrostrictive device of the present invention;

FIGS. 9(a) to 9(c) show still another embodiment of apiezoelectric/electrostrictive device of the present invention, in which

FIGS. 9(a) and 9(b) are top views of the embodiment and FIG. 9(c) is asectional view of the embodiment;

FIGS. 10(a)-(d) show top views of still another embodiment of apiezoelectric/electrostrictive device of the present invention;

FIGS. 11 (a)-(b) show top views of still another embodiment of apiezoelectric/electrostrictive device of the present invention;

FIG. 12 shows perspective views of an embodiment of an actuator to whicha piezoelectric/electrostrictive device of the present invention isapplied;

FIG. 13 shows a top view of still another embodiment of apiezoelectric/electrostrictive device of the present invention;

FIG. 14 shows a top view of still another embodiment of apiezoelectric/electrostrictive device of the present invention;

FIGS. 15(a)-(c) show top views of still another embodiment of apiezoelectric/electrostrictive device of the present invention;

FIGS. 16(a) and 16(b) show still another embodiment of apiezoelectric/electrostrictive device of the present invention, in whichFIG. 16(a) is a top view of the embodiment and FIG. 16(b) is a sectionalview of the embodiment;

FIG. 17 shows a top view of still another embodiment of apiezoelectric/electrostrictive device of the present invention;

FIGS. 18(a) to 18(d) show still another embodiment of apiezoelectric/electrostrictive device of the present invention, in whichFIG. 18(a) is a top view of the embodiment and FIGS. 18(b) to 18(d) aresectional views of the embodiment;

FIGS. 19(a)-(b) show top views of still another embodiment of apiezoelectric/electrostrictive device of the present invention;

FIGS. 20(a)-(c) show top views of still another embodiment of apiezoelectric/electrostrictive device of the present invention;

FIGS. 21(a) to 21(f) show still another embodiment of a piezoelectric/electrostrictive device of the present invention, in which FIGS. 21(a)to 21(d) and FIG. 21(f) are top views of various structures respectivelyconstituted by joining a diaphragm with a connection plate and FIG.21(e) is a top view of a structure constituted by joining a diaphragmwith a fixing plate;

FIG. 22 shows top views of worked green sheets for substrates used tofabricate a piezoelectric/electrostrictive device of the presentinvention;

FIG. 23 shows illustrations of a method for working a piezoelectricelement of a piezoelectric/electrostrictive device of the presentinvention;

FIG. 24 shows a perspective view of a structure of a conventionalpiezoelectric/electrostrictive device (piezoelectric actuator); and

FIG. 25 shows a top view of still another embodiment of apiezoelectric/electrostrictive device of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1(a) is a perspective view of an embodiment of apiezoelectric/electrostrictive device 50A of the present invention. Thepiezoelectric/electrostrictive device 50A has a shape in which apiezoelectric element 55 comprising a first electrode 52, apiezoelectric film 53, and a second electrode 54 is provided for oneplane of a diaphragm 51 whose one side is joined to a substrate 49 andone side of a thin fixing plate 56 is joined to one side of thediaphragm 51 so that the plane of the fixing plate 56 and the plane ofthe diaphragm 51 are perpendicular to each other. In this case, it isalso possible to provide the piezoelectric element 55 on both planes ofthe diaphragm 51 and thus, a lead portion (not illustrated) to be usedfor connection with a driving power supply or the like is connected tothe first electrode 52 and the second electrode 54. Moreover, a side ofthe diaphragm 51 represents a plane vertical to the plane of thediaphragm 51 where the piezoelectric element 55 is set, that is, thethickness-directional plane and one side represents either of the sides.

By using the structure shown by the piezoelectric/electrostrictivedevice 50A, it is possible to displace the fixing plate 56 in the planedirection of the fixing plate 56 mainly. Specifically, the following aretypical displacement modes: a displacement mode in which, when assumingthe connection face between the fixing plate 56 and diaphragm 51 in FIG.1(a) as a fixed plane, the fixing plate 56 displaces like a pendulum inthe direction vertical to the side of the fixing plate 56 and verticalto Y-axis, that is, in X-axis direction centering around the verticalaxis (Y-axis) vertically passing through the center of the fixed plane(this displacement mode is hereafter referred to as “θ mode”), adisplacement mode in which the fixing plate 56 displaces like a pendulumin X-axis direction centering around Y-axis so that the component ofswing in Z-axis direction parallel with the side of the fixing plate 56increases as away from Y-axis (this displacement mode is hereafterreferred to as “φ mode”), and a telescopic displacement mode in Y-axisdirection.

These displacement modes represent that the displacement direction ofthe fixing plate 56 is dominant in the above-described directions but adirectional component other than described directions is not completelyexcluded. The same is true for a case of referring to displacement modesof various embodiments described below.

When considering application of a magnetic head, it is preferable thatthe head does not exhibit three-dimensional displacement so as to keepthe space (gap) between the head and a recording medium. Thepiezoelectric/electrostrictive device 50A displacing in the θ mode ortelescopic displacement mode is a device suitable for the above purpose.When using the piezoelectric/electrostrictive device 50A for anacceleration sensor other than a magnetic head, it is a matter of courseto use the φ mode in addition to the above modes. The relation betweenthe dimension of each displacement mode and a purpose is common to theconfiguration of every piezoelectric/electrostrictive device of thepresent invention.

FIGS. 1(b) to 1(d) show other embodiments using the operation principleof the piezoelectric/electrostrictive device 50A. Here, thepiezoelectric/electrostrictive device 50B shown in FIG. 1(b) isconfigured by setting two fixing plates 56 in FIG. 1(a) to one side ofthe diaphragm 51 in parallel. Therefore, it is possible to use aplurality of fixing plates 56 and thus, it is possible to use anecessary number of fixing plates according to the purpose.

Joining positions between a plurality of fixing plates 56 and thediaphragm 51 can be set to any side other than the joining side betweenthe substrate 49 and the diaphragm 51. Moreover, it is enough that atleast one fixing plate 56 is set. Therefore, in case of thepiezoelectric/electrostrictive device 50C shown in FIG. 1(c), it is alsopossible to join the fixing plate 56 to the side vertical to the joiningside between the diaphragm 51 and the substrate 49 among the sides ofthe diaphragm 51. Moreover, in case of thepiezoelectric/electrostrictive device 50D shown in FIG. 1(d), it ispossible to set two fixing plates 56 on opposite sides of diaphragm 51.

The laminar-type configuration obtained by forming the first electrode52, piezoelectric film 53, and second electrode 54 into a layer shown inFIG. 2 is typical as the configuration of the piezoelectric element 55used for the piezoelectric/electrostrictive devices 50A to 50D describedabove. Moreover, as shown in FIG. 3, it is possible to use apiezoelectric element 62A having comb-shaped electrodes in which apiezoelectric film 58 is formed on a diaphragm 57 and a first electrode59 and a second electrode 60 form a gap portion 61 having a certainwidth on the piezoelectric film 58. The first electrode 59 and secondelectrode 60 in FIG. 3 can be also formed between the diaphragm 57 andthe piezoelectric film 58. Moreover, as shown in FIG. 4, a piezoelectricelement 62B is preferably used which is configured by embedding thepiezoelectric film 58 between the comb-shaped first electrode 59 andsecond electrode 60.

In this case, when using the comb-shaped electrodes shown in FIGS. 3 and4, it is possible to increase a displacement by decreasing a pitch 63.The piezoelectric elements shown in FIGS. 2 to 4 can be applied to everypiezoelectric/electrostrictive device of the present invention to bementioned later.

The piezoelectric/electrostrictive devices 50A to 50D described aboveare disadvantageous for decrease in size and weight and moreover, easilycause a trouble that a warpage or curve occurs on the fixing plate 56and it is difficult to adjust a displacement mode. Therefore, it ispreferable to use the devices 50A to 50D by changing their structures tothe structure shown in FIG. 5(a) because these problems are solved.

FIG. 5(a) is a top view of another embodiment of apiezoelectric/electrostrictive device of the present invention. Thepiezoelectric/electrostrictive device 30 has a structure in which afixing plate 31 and a connection plate 33 are joined with each other attheir sides, a diaphragm 32 is joined to the connection plate 33 attheir sides in the direction perpendicular to the Y-axis directionserving as the direction of joining between the fixing plate 31 and theconnection plate 33, that is, the X-axis direction, a piezoelectricelement 35 is set on one plane of the diaphragm 32, and parts of sidesof the connection plate 33 and diaphragm 32 are joined to a side of thesubstrate 34. In this case, it is also possible to form thepiezoelectric element 35 on the both planes of the diaphragm 32 and useone of the above-described various piezoelectric elements shown in FIGS.2 to 4 as the piezoelectric element 35.

It is not always necessary for the fixing plate 31, connection plate 33,and diaphragm 32 to have the same thickness. This is because any one ofvarious shapes can be selected as the shape of the fixing plate 31 asdescribed later. However, it is preferable to integrally form the fixingplate 31, connection plate 33, and diaphragm 32 and moreover, it ispreferable to form a side of the connection plate 33 and the diaphragm32 integrally with the substrate 34. This integral structure can beeasily obtained through the lamination method using ceramic green sheetsto be mentioned later.

It is possible to operate the piezoelectric/electrostrictive device 30in at least any one of the bending mode in which the fixing plate 31displaces so as to bend in the Z-axis direction (not illustrated)vertical to the X-axis and the Y-axis, the axis rotation mode in whichthe fixing plate 31 displaces so as to rotate by using the Y-axis as abase axis, the θ mode in which the fixing plate 31 displaces like apendulum in the X-axis direction so that the fixing plate 31 forms acertain angle θ from the Y-axis centering around the Y-axis in the planeof the plate 31, and the φ mode in which the fixing plate 31 displaceslike a pendulum in the X-axis direction centering around the Y-axis sothat the component of swing in the Z-axis direction (not illustrated)parallel with a side of the fixing plate 31 increases as away from theY-axis.

The above θ mode and φ mode are described below in more detail. FIG.5(b) is a top view for explaining the θ mode, which shows movement ofthe fixing plate 31 when viewing the piezoelectric/electrostrictivedevice 30 in FIG. 5(a) from the direction of arrows AA in FIG. 5(a),that is, from the Y-axis direction on the X-axis. In this case, theupper end face 31F of the fixing plate 31 is present at a position P1when it does not displace. As described above, however, in the θ mode,the fixing plate 31 displaces like a pendulum in the X-axis directioncentering around the Y-axis in the plane of the fixing plate 31, thatis, the X-Y plane so as to form a certain angle θ from the Y-axis. Inthis case, from the direction of arrows AA, it is possible to show themovement of the upper end face 31 F of the fixing plate 31 as adisplacement reciprocating between positions P2 and P3 on the X-axis andthe displacement motion is defined as θ mode.

FIG. 5(c) is a top view for explaining the φ mode and shows the movementof the fixing plate 31 when viewing the piezoelectric/electrostrictivedevice 30 in FIG. 5(a) from the direction of arrows AA in FIG. 5(a)similarly to the case of FIG. 5(b). Also in FIG. 5(c), the upper endface 31F of the fixing plate 31 is present at the position P1 when itdoes not vibrate. As described above, in the φ mode, the fixing plate 31displaces like a pendulum centering around the Y-axis in the X-axisdirection and displaces so that the component of swing in the Z-axisdirection parallel with a side of the fixing plate 31 increases as awayfrom the Y-axis. That is, the movement of the upper end face 31F of thefixing plate 31 from the direction of arrows AA is shown as adisplacement reciprocating between a position P4 and a position P5 on acircular-arc orbit S passing through the position P1 when assuming apoint on the Z-axis as center O. In this case, an angle formed betweenthe straight line connecting the fixing plate 31 and the center O andthe Z-axis is φ and the above displacement motion is defined as φ mode.

In the case of the piezoelectric/electrostrictive device 30, it is alsopossible to divide one piezoelectric element 35 so that twopiezoelectric elements 35A and 35B are formed in the Y-axis direction.Moreover, it is possible to set two piezoelectric elements on the bothplanes of the diaphragm 32 one each. In this case, it is preferable touse one piezoelectric element 35A as a driving element to make thefixing plate 31 cause a predetermined displacement and the otherpiezoelectric element 35B as an auxiliary element, for example, forconfirming whether a predetermined displacement amount is obtained, thatis, an auxiliary element is preferably used as a displacementconfirmation/decision element, trouble-shooting element, or auxiliarydriving element for detecting the displacement of the drivingpiezoelectric element 35A and applying feedback to driving signals forthe driving piezoelectric element 35A so that a predetermineddisplacement can be obtained when a voltage applied to the drivingpiezoelectric element 35A does not reach a predetermined voltage amountdue to any cause, because the driving accuracy, positional accuracy, anddetection accuracy can be improved.

To divide one piezoelectric element 35, it is possible to use any one ofa method for setting the element 35 and thereafter dividing the element35 through laser-beam processing and a method for dividing thepiezoelectric element 35 and thereafter setting it. The arrangement of aplurality of piezoelectric elements and the division and usage of eachpiezoelectric element 35 can be applied to everypiezoelectric/electrostrictive device of the present invention.

The shape of the plane of the fixing plate 31 of the abovepiezoelectric/electrostrictive device 30 is not restricted to therectangle shown in FIG. 5(a). As shown by thepiezoelectric/electrostrictive devices 30A to 30C in FIGS. 6(a) to 6(c),it is possible to use various optional shapes such as circle, triangle,inverse-concave shape, polygon, ellipse, and long circle. Moreover, itis unnecessary to join the fixing plate 31 so as to be symmetric to theconnection plate 33 with respect to the Y-axis as shown by thepiezoelectric/electrostrictive device 30D in FIG. 6(d). That is, it ispossible to optionally select the shape of the fixing plate 31 inaccordance with various sensors, a recording head, or other structuresused in combination with the piezoelectric/electrostrictive device.

Then, in the case of the present invention, it is possible to preferablyuse a structure in which a spring plate is bonded with one plane or bothplanes of a connection plate and the spring plate is joined to a sensorsubstrate or a spring-plate reinforcement portion. FIG. 7(a) is a topview of a piezoelectric/electrostrictive device 40A which is anembodiment constituted by setting a prismatic spring plate 38 and aspring-plate reinforcement portion 39 to the abovepiezoelectric/electrostrictive device 30. Moreover, FIGS. 7(b) to 7(e)are sectional views showing the arrangement of the spring plate 38 andthe spring-plate reinforcement portion 39 viewed from the X-axisdirection on the Y-axis.

The spring plate 38 is joined to at least one plane of the connectionplate 33 and its width can be narrower than or equal to that of theconnection plate 33 as shown in FIG. 7(a). Moreover, to set the springplates 38 made of the same material to the both plane of the connectionplate 33 one each, it is preferable to equalize the shapes of the springplates 38. However, to apply spring plates 38 made of materialsdifferent from each other to planes of the connection plate 33 one each,it is unnecessary to equalize the shapes of the spring plates 38 eachother. It is possible to form each spring plate 38 into a proper shapeby considering the Young's modulus of each spring plate 38.

The spring plate 38 is also joined to the substrate 34 in principle. Inthis case, it is decided whether it is necessary or not to set thespring-plate reinforcement portion 39 depending on the joining positionof the connection plate 33 with the substrate 34. That is, as shown inFIGS. 7(b) and 7(c), when the connection plate 33 is joined to aposition where the spring plate 38 can be directly joined to thesubstrate 34, it is unnecessary to separately set the spring-platereinforcement portion 39 because the substrate 34 also functions as thespring-plate reinforcement portion 39. Moreover, in this case, it ispossible to set the spring plate 38 only to one plane of the connectionplate 33.

However, as shown in FIG. 7(d), when the connection plate 33 is joinedto an end of the substrate 34, it is preferable to set the spring-platereinforcement portion 39 to the spring plate 38B as a portion forsupporting the spring plate 38B though the substrate 34 also functionsas the spring-plate reinforcement portion 39 in the case of the springplate 38A. Moreover, as shown in FIG. 7(e), even when the connectionplate 33 is joined to an end of the substrate 12, it is not necessary toform the spring-plate reinforcement portion 39 when only the springplate 38A is joined to the substrate 12 and the spring plate 38B is notused.

By setting the spring plate 38, the mechanical strength of theconnection plate 33 is improved. Moreover, in case of setting the springplate 38 to the both planes of the connection plate 33, it is possibleto displacement the center of gravity of a portion constituted of theconnection plate 33 and the spring plate 38 when displacing the fixingplate 31 by the piezoelectric/electrostrictive device 35. Therefore, thefixing plate 31 is easily displaced to the θ mode and this is preferablefor the purpose such as a magnetic head or the like. Moreover, anadvantage of improving the rigidity and the high-speed responsecharacteristic of a piezoelectric/electrostrictive device can beobtained.

That is, as sectional views viewed from the Y-axis direction on theX-axis in FIGS. 7(c) and 7(d) are shown in FIGS. 8(a) and 8(b), thefixing plate 31 easily displaces in the X-axis direction, that is in theθ mode in FIG. 8(a) because the piezoelectric/element 35 is able todisplace the center O of the spring plates 38A and 38B and theconnection plate 33 in the X-axis direction. However, in FIG. 8(b),since the center O of the spring plates 38A and 38B and the connectionplate 33 is not present on the connection plate 33, the driving force ofthe piezoelectric element 35 in the X-axis direction (arrow S₁) is addedto the center O as a torque (arrow S₂) and the displacement of the axisrotation mode easily occurs though the rotation mode is restricted dueto the rigidity of the spring plate 38A.

Thus, when setting the spring plate 38, it is preferable to further seta reinforcement plate 41 to be bonded with the spring plate 38 andjoined to a side of the substrate 34 like the case of thepiezoelectric/electrostrictive device 40B shown in FIG. 9. Here, FIGS.9(a) and 9(b) show top views of the piezoelectric/electrostrictivedevice 40B viewed from the surface and the back of it and FIG. 9(c)shows a sectional view of the device 40B viewed from the Y-axisdirection on the X-axis in FIG. 9(b). In this case, the reinforcementplate 41 is bonded to the spring plate 38A bonded to the connectionplate 33 and joined to the squarely-cut-out side of the substrate 34.Moreover, it is preferable that the reinforcement plate 41 is formedintegrally with the spring plate 38 and the substrate 34.

It is needless to say that the above spring plate can be applied toevery piezoelectric/electrostrictive device of the present invention inwhich a connection plate is used as a component member. Moreover, asdescribed later in a method for fabricating apiezoelectric/electrostrictive device of the present invention, it ispreferable that the spring plate is formed integrally with anintermediate plate inserted between and integrated with a diaphragmplate and a base plate or formed integrally with a spring-platereinforcement portion formed integrally with the diaphragm plate andalso formed integrally with each connection plate.

FIGS. 10(a) to 10(d) show still another embodiment of apiezoelectric/electrostrictive device of the present invention. FIG.10(a) shows a sectional view of a piezoelectric/electrostrictive device11A and a sectional view taken along the broken line A—A of the topview. In the case of the piezoelectric/electrostrictive device 11A, aspring plate 38 is bonded to a connection plate 33 and a fixing plate 31has a shape formed by extending the connection plate 33 and the springplate 38 in the Y-axis direction. Therefore, the boundary between thefixing plate 31 and the connection plate 33 or the spring plate 38 isnot clear. A structure obtained by integrating the fixing plate 31,connection plate 33, and spring plate 38 is the same as the case of thepiezoelectric/electrostrictive devices 11B to 11D shown in FIGS. 10(b)to 10(d) and hereafter referred to as a connection-fixing plate 36. Byforming the connection-fixing plate 36 into a thick and slender shape,it is possible to prevent displacement modes such as bending mode andaxis rotation mode from occurring.

In the case of the piezoelectric/electrostrictive device 11B shown inFIG. 10(b), a constricted portion 37 is provided for theconnection-fixing plate 36. Moreover, in the case of thepiezoelectric/electrostrictive device 11C shown in FIG. 10(c), a slit 48is formed for the connection-fixing plate 36. By forming the constrictedportion 37 and/or the slit 48, the rigidity of the connection-fixingplate 36 decreases and it is possible to further increase thedisplacement amount at the front end of the connection-fixing plate 36.Furthermore, in the case of the piezoelectric/electrostrictive device11D shown in FIG. 10(d), it is preferable to form the slit 48 at thefront end side of the connection-fixing plate 36, preferably at thefront end side of the joint between the diaphragm 32 and theconnection-fixing plate 36 because the weight of thepiezoelectric/electrostrictive device 11D itself can be decreasedwithout greatly changing characteristics of thepiezoelectric/electrostrictive device.

FIG. 11(a) shows a top view of a piezoelectric/electrostrictive device12A in which the shape of the above connection-fixing plate 36 ischanged and a sectional view taken along the broken line A—A of the topview. The connection-fixing plate 36 of thepiezoelectric/electrostrictive device 12A is formed so that thecircumferential portion of the connection-fixing plate is thicker thanthe central portion of connection-fixing plate. The shape of theconnection-fixing plate 36 can be regarded as a structure constituted bythinning the central portion of the connection-fixing plate 36 of thepiezoelectric/electrostrictive device 11A, and the fixing plate can beobtained by bonding a predetermined U-shaped spring plate 38 to theplane of a thin connection-fixing plate. Thepiezoelectric/electrostrictive device 12A is strong against twist thoughit is decreased in weight. Therefore, it is possible to improve thepositioning speed (improvement of displacement-amount controllability)and the displacement (movement) path accuracy. Moreover, as thepiezoelectric/electrostrictive device 12B shown in the top view of FIG.11(b), it is possible to form the slit 48 at a portion of the connectionfixing-plate 36 of the piezoelectric/electrostrictive device 12A wherethere is not the spring plate 38 (hollow portion inside of the U-shapedspring plate 38) and thereby, it is possible to increase a displacementamount.

FIG. 25 is a top view of still another piezoelectric/electrostrictivedevice 12C using the above connection-fixing plate 36, showing anembodiment constituted by joining other diaphragm on which apiezoelectric element is formed to one end of a fixing plate at theirsides and alternately joining necessary numbers of other connectionplates and/or other fixing plates and still other diaphragms with theabove other diaphragm at their sides.

That is, the piezoelectric/electrostrictive device 12C has a structurein which a first diaphragm 32A and a first connection-fixing plate 36Aare joined to a side of the substrate 34, a second diaphragm 32B isjoined to the side of the open side (normal fixing plate setting side)of the first connection-fixing plate 36A, and second connection-fixingplate 36B, third diaphragm 32C, and third connection-fixing plate 36Care successively joined to the second diaphragm 32B at their sides.Thus, by driving piezoelectric elements 35A to 35C arranged on the firstto third diaphragm, it is possible to increase the displacement amountof the third connection plate 36C in the X-axis direction in FIG. 25.

The above structure can be also regarded as a structure obtained bysuccessively joining a unit comprising a set of a diaphragm and aconnection-fixing plate such as the second diaphragm 32B and the secondconnection-fixing plate 36B. Therefore, to obtain a predetermineddisplacement amount, it is only necessary to properly set the number ofunits to a preferable number.

FIG. 12 shows perspective views of an actuator 26 using theabove-described piezoelectric/electrostrictive device 11A. Thepiezoelectric/electrostrictive device 11A is firmly fixed to a membersuch as a slider 27 by a fixing jig 29 or the like. A magnetic head 13is set to the front end of the connection-fixing plate 36 of thepiezoelectric/electrostrictive device 11A and it is possible to move thehead 13 by a predetermined displacement amount by driving thepiezoelectric element 35. Moreover, it is possible to unite a member tobe fixed such as the slider 27 and the piezoelectric/electrostrictivedevice 11A into one body by processing green sheets to be describedlater without using the fixing jig 29.

FIG. 13 shows an embodiment obtained by setting thepiezoelectric/electrostrictive device 11A to two places in the substrate34. It is possible to use the piezoelectric/electrostrictive devices 11Aset to two places for the same purpose or different purposes at the sametime and for a purpose of setting one piezoelectric/electrostrictivedevice 11A as a spare when the other piezoelectric/electrostrictivedevice 11A is broken. Therefore, it is possible to set a plurality ofpiezoelectric/electrostrictive devices of the present invention in onesubstrate and the setting positions of them are not restricted to thetransverse parallel position shown in FIG. 13.

FIG. 14 is a top view of still another embodiment of apiezoelectric/electrostrictive device of the present invention. Theabove-described piezoelectric/electrostrictive device 30 has a structurein which the diaphragm 32 and the substrate 34 are joined each otheronly by one side. In the case of a piezoelectric/electrostrictive device42, however, a diaphragm 21 and a substrate 2 are joined each other bytwo sides and one side is joined to a connection plate 20. By applyingthe above structure, it is possible to control the bending of theconnection plate 20 and/or a spring plate 18 and easily cause a θ-modedisplacement in the fixing plate 19.

FIGS. 15(a) to 15(c) are top views of piezoelectric/electrostrictivedevices 43A to 43C showing still another embodiment. First, thepiezoelectric/electrostrictive device 43A shown in FIG. 15(a) has astructure in which a connection plate 20 and a fixing plate 19 arejoined to each other at their sides, two diaphragm 2 1A and 21B arejoined to the connection plate 20 at their sides so as to hold theconnection plate 20 in the direction perpendicular to the direction ofconnection between the fixing plate 19 and the connection plate 20, andmoreover, the diaphragm 21A and 21B are also joined to the substrate 2similarly to the case of the diaphragm 21 shown in FIG. 14 and supportedand fixed by three sides. By this structure, three-dimensionaldisplacement modes such as the bending mode and the axis rotation modeof the fixing plate 19 are restricted. Moreover, it is not alwaysnecessary to join the diaphragm 21A and 21B to the substrate 2 at thebottom of the concave potion of the substrate 2.

In the case of the piezoelectric/electrostrictive device 43A, fourpiezoelectric elements 25A to 25 d are formed on the both planes of the21A and 21B. By properly assigning these piezoelectric elements to thedriving element and auxiliary element for the fixing plate 19,more-accurate displacement control is realized.

Then, the piezoelectric/electrostrictive device 43B shown in FIG. 15(b)has a structure obtained by superimposing at least one of thepiezoelectric elements 25A to 25D of the piezoelectric/electrostrictivedevice 43A, for example, at least one direction of the piezoelectricelements 25C and 25D on one side or two sides of substrate-2 side of theabove three-side-supported diaphragm. In this case, it is preferable touse the piezoelectric elements 25C and 25D as auxiliary elements formeasurement such as displacement-amount detection or troubleshootingbecause high accuracy measurement is realized. Even when displacingsetting positions of the piezoelectric elements 25A to 25D, it isnecessary that the piezoelectric elements 25A to 25D do not overhang theconnection plate 20 or a spring plate when the spring plate is used.

When bonding a spring plate to the connection plates 20 of thepiezoelectric/electrostrictive devices 43A and 43B, it is possible touse a spring-plate reinforcement portion or reinforcement platesimilarly to the case of the piezoelectric/electrostrictive device 40B.In this case, it is necessary to form the reinforcement plate so that itis joined at three sides of the substrate 2 serving as joining sidesbetween the diaphragm 21A and 21B, connection plate 20, and substrate 2.

The piezoelectric/electrostrictive device 43C shown in FIG. 15(c) is anembodiment constituted by forming a slit 48 at the central portion inthe longitudinal direction of the connection plate 20 of thepiezoelectric/electrostrictive device 43A. The slit 48 is hollow and hasa function for increasing the displacement amount of the diaphragm 19and easily causing displacement or oscillation in ν mode or νz mode.

Here, the ν mode represents a mode in which the diaphragm 19 displacesso as to swing in the X-axis direction. When comparing the ν mode withthe θ mode, the θ mode shows a pendulum-like displacement in the X-Yplane and has a Y-axis-directional component. In the case of the v mode,however, a uniaxial-directional displacement in the X-axis direction inthe X-Y plane is dominant and different from the θ mode in that ithardly has a Y-axis-directional component. Moreover, the νz moderepresents a mode greatly displacing in the Z-axis direction (directionvertical to the X-axis and the Y-axis) as the diaphragm 19 away from theY-axis in the displacement mode in the ν mode. When comparing the νzmode with the φ mode, it is different from the φ mode in that it hardlyhas a Y-axis directional component.

Because of the above displacement mode, it is difficult to use the νmode and the νz mode for static displacement control. However, it ispossible to use the modes for a dynamic displacement such asoscillation- and a displacement caused by an external stress.

When setting a diaphragm to two places so as to hold a connection plateas shown in the case of the piezoelectric/electrostrictive devices 43Ato 43C, it is possible to change the lengths N₁ and N₂ of the diaphragm21A and 21B and the widths M₁ and M₂ of them and thereby increase thedriving force of the fixing plate 19 by increasing the area of onediaphragm and preferably use the other diaphragm as an auxiliary elementsuch as a displacement monitor by decreasing the area of the otherdiaphragm as shown by the top view in FIG. 16(a). Moreover, whenchanging the widths M₁ and M₂ of the diaphragm 21A and 21B, it ispossible to improve the displacement accuracy and measurement accuracyby changing proper oscillation number of the bending displacement mode{arrow G in FIG. 16(b)) of the diaphragm 21A and 21B determined by thepiezoelectric elements 25A and 25B and the diaphragm 21A and 21B to f₁,and f₂ and using one as a driving element and the other as an auxiliaryelement. It is preferable to use a piezoelectric element having smallerone of the proper oscillation number f₁, and f₂ as a driving element anda piezoelectric element having larger one of the frequencies f₁ and f₂as an auxiliary element.

As shown by the case of the piezoelectric/electrostrictive devices 43Ato 43C shown in FIG. 15 or 16, when setting a diaphragm to two places soas to hold a connection plate, it is more preferable to form a structurein which at least either of the piezoelectric elements 25C and 25D isformed on one diaphragm such as the diaphragm 21B and one slit 28 orpreferably more slits 28 is or are formed on the other diaphragm 21A inthe direction vertical to the direction of joining between the diaphragm21A and the connection plate 20 as shown in FIG. 17. By using the abovestructure, it is possible to restrict rotations and vibrations and makea displacement in the θ mode dominant.

FIG. 18(a) shows a top view of a piezoelectric/electrostrictive device43D in which the piezoelectric/electrostrictive device 43A of FIG. 15(a)is formed on the through-hole 14 of a substrate 2 and FIGS. 18(b) to18(d) show sectional views taken along the broken line A—A in FIG.18(a). In the case of the piezoelectric/electrostrictive device 43D, twopiezoelectric elements 25A and 25C are arranged and provided withelectrode leads 9 and 10. Moreover, an insulating coating layer 65 isformed so as to cover the piezoelectric elements 25A and 25C and theelectrode leads 9 and 10. The insulating coating layer 65 respectivelyhave a function for effectively preventing the piezoelectric elements25A and 25C and the electrode leads 9 and 10 from being short-circuitedwhen using a fixing plate 19 and the piezoelectric elements 25A and 25Cin a liquid atmosphere or humidified atmosphere.

Furthermore, a shielding layer 66 made of a conductive material isformed on the piezoelectric/electrostrictive device 43D so as to coverthe insulating coating layer 65 and formed on the both sides of thesubstrate 2 through a through-hole 67. The shielding layer 66 hasfunctions for cutting off external electromagnetic waves when operatinga piezoelectric/electrostrictive device at a high frequency or detectinghigh-frequency oscillation to preferably secure the displacementaccuracy and moreover preventing erroneous operations from occurring ornoises from mixing.

Configurations of setting the shielding layer 66 include theconfiguration of forming the shielding layer 66 so as to hold thesubstrate 2 as shown in FIG. 18(b), the configuration of enclosing onlythe wiring portion on the substrate 2 as shown in FIG. 18(c), and theconfiguration of shielding the wiring portion with only upper eitherside. Particularly, however, the configuration of shielding the entirewiring portion shown in FIGS. 18(b) and 18(c) is preferable. In FIG.18(a), shielding layers 66 formed on the planes of the substrate 2 areelectrically connected by using a through-hole 67. However, it is alsopossible to electrically connect them by using a side of the substrate2. Details of materials preferably used to form the insulating coatinglayer 65 and the shielding layer 66 are described when the material of apiezoelectric/ electrostrictive device is described later.

FIGS. 19(a) and 19(b) are top views of embodiments of still anotherpiezoelectric/electrostrictive devices of the present invention. Thepiezoelectric/electrostrictive device 44A shown in FIG. 19(a) has astructure in which a connection plate 20 and a diaphragm 21 with apiezoelectric element 25 set on it are joined to a fixing plate 19 attheir sides in parallel without being joined each other and theconnection plate 20 and the diaphragm 21 are joined to a side of asubstrate 2 while the fixing plate 19 is not joined to the substrate 2.The diaphragm 21 also functions as the connection plate 20. However, thepiezoelectric/electrostrictive device 44B shown in FIG. 19(b) has astructure in which two diaphragm 21A and 21B are arranged at the bothsides of a connection plate 20 and piezoelectric elements 25A and 25Bare arranged on the diaphragm 21A and 21B.

The piezoelectric/electrostrictive devices 44A and 44B are suitable fordisplacement and measurement in the θ mode because the displacement ofthe fixing plate 19 easily occurs in the plane of the fixing plate 19and rotation and vibration of the fixing plate 19 are restricted.Moreover, because a strain generated by the piezoelectric element 25directly works on the fixing plate 19 through the diaphragm 21 orbecause of its inverse action, there is an advantage that the positionalaccuracy and sensing sensitivity are improved.

FIGS. 20(a) to 20(c) are top views of embodiments of still anotherpiezoelectric/electrostrictive devices of the present invention. First,in the case of the piezoelectric/electrostrictive device 45A shown inFIG. 20(a), a fixing plate 72 is joined to two connection plates 74A and74B at their sides so as to be held by the connection plates 74A and 74Band sides of the connection plates 74A and 74B are set between the sidesof a concave portion 76 of a substrate 70, two diaphragm 73A and 73B areset between the connection plates 74A and 74B and between the bottomsides of the concave portion 76 in the direction for the connectionplates 74A and 74B to hold the fixing plate 72, that is, the directionperpendicular to the Y-axis direction, and moreover piezoelectricelements 75A and 75B are arranged on one plane of each of the diaphragm73A and 74B. By using the above structure, an advantage is obtained thatbending of the fixing plate 72 is controlled.

The concave portion 76 can use a side of the through-hole 14 formed onthe substrate 2 previously shown in FIG. 18 or can be formed by cuttingout a part of the outer periphery of the substrate 70. Moreover, theshape of the fixing plate 72 is not restricted to a rectangle. It ispossible to use one of the fixing plates of optional shapes shown inFIGS. 6(a) to 6(d).

The piezoelectric/electrostrictive device 45B shown in FIG. 20(b) isconstituted by joining a fixing plate 72 with connection plates 74A and74B so as to separate the fixing plate 72 far from diaphragm 73A and73B, which is effective to increase a displacement amount. Thus, asetting position of the fixing plate 72 can be optionally selected.Moreover, the piezoelectric/electrostrictive device 45C shown in FIG.20(c) shows an embodiment in which diaphragm 73A and 73B are supportedand fixed by connection plates 74A and 75B and a substrate 70 at threesides similarly to the case of the diaphragm 21 shown in FIG. 14.

These piezoelectric/electrostrictive devices 45A to 45C respectivelyhave a preferable structure to perform displacement control ordisplacement-amount measurement in at least any one of the displacementmodes such as the θ mode in which the fixing plate 72 displaces like apendulum in the X-axis direction vertical to a side of the fixing plate72 and vertical to the Y-axis centering abround the Y-axis which is anaxis vertically passing through the center of the fixed plane by usingthe joining face between the fixing plate 72 and the connection plate74A or 74B, the φ mode in which the fixing plate 72 displaces like apendulum centering around the Y-axis while a swing in the the X-axisdirection is followed by a swing in the Z-axis direction (notillustrated) which is the direction parallel with a side of the fixingplate 72, a mode in which the fixing plate 72 displaces in the X-axisdirection centering around the Y-axis shown by the bidirectional arrow Kin FIG. 20(a) (hereafter, this mode is defined as “κ mode”), or arotation mode in the plane of the fixing plate 72. Particularly, astable displacement can be obtained in the κ mode.

Piezoelectric/electrostrictive devices 46A to 46F, which are still otherembodiments of the present invention shown by top views in FIGS. 21(a)to 21(f) respectively, have a structure in which a fixing plate 72 isjoined to two connection plates 74A and 74B at their sides so as to beheld by the connection plates 74A and 74B, sides of the connectionplates 74A and 74B are set between the sides of a through-hole 71 of asubstrate 70 having through-holes, and at least a plurality ofdiaphragm, that is, diaphragm 73A to 73D in this case are set betweenthe sides of the connection plates 74A and 74B and the through-hole 71or the sides of the fixing plate 72 and the through-hole 71 in thedirection vertical to the direction in which the fixing plate 72 is heldby connection plates 74A and 74B. Piezoelectric elements 75A to 75D areoptionally arranged on at least a portion on at least one plane of atleast one of the diaphragm 73A to 73D.

In the case of each of the piezoelectric/electrostrictive devices 46A to46F, when comparing the structure of the piezoelectric/electrostrictivedevice 46A with those of the piezoelectric/electrostrictive devices 45Ato 45C shown in FIGS. 20(a) to 20(c), rotation of the fixing plate 72centering around the Y-axis is restricted by the diaphragm 73A and 73B.Moreover, by forming the slit 28 on the diaphragm 73A and 73B similarlyto the case of FIG. 17, the fixing plate 72 can easily displace in thedirection of the arrow K, that is, a κ-mode displacement can be easilyobtained.

The piezoelectric/electrostrictive device 46B is constituted byarranging the piezoelectric elements 75A to 75D on same-directionalplanes of all the diaphragm 73A to 73D. By using these piezoelectricelements as driving elements, it is possible to increase thedisplacement amount of the fixing plate 72 in the K direction. Moreover,the piezoelectric elements 75A to 75D can be provided for both planes ofthe diaphragms 73A to 73D and it is also preferable to use piezoelectricelements arranged in the same direction as auxiliary elements.

The piezoelectric/electrostrictive device 46C shows an embodiment formedso that sides of the diaphragm 73A to 73D in FIGS. 21(a) and 21(b)facing the substrate 70 are joined to the substrate 70. By using theabove structure, it is possible to add the advantages obtained from thestructure shown in FIG. 14 to those of FIGS. 21(a) and 21(b).

The piezoelectric/electrostrictive device 46D is constituted byarranging the piezoelectric elements 75B and 75C on the diaphragm 73Band 73C present at positions symmetric to the intersection between theX-axis and the Y-axis, which is the center of the fixing plate 72. Inthis case, as the displacement mode of the fixing plate 72, it ispossible to use a displacement mode in which a displacement in the ηdirection {the direction of the bidirectional arrow in FIG. 21(d)}centering around the intersection between the X-axis and the Y-axis.Because the displacement mode is a rigid-body mode, it is not alwaysnecessary to form the diaphragm 73A and 73D. Moreover, when thediaphragm 73A and 73D are formed, it is possible to form the slit 28 orthe piezoelectric elements 73A and 73D on the diaphragm 73A and 73D.

The piezoelectric/electrostrictive device 46E is constituted by joiningthe diaphragm 73A to 73D to the fixing plate 72, in which the settingstate of the piezoelectric elements 75A to 75D is the same as the caseof FIG. 21(b). By using the above structure, it is possible to generateor measure the displacement of the fixing plate 72 in the κ mode.Moreover, the piezoelectric/electrostrictive device 46F has a structureto be easily displaced in the θ and φ modes by increasing one widths ofthe connection plates 74A and 74B and decreasing the other widths ofthem.

As described above, for piezoelectric/electrostrictive devices of thepresent invention, it is possible to select various shapes but materialsused for piezoelectric/electrostrictive devices are not different ineach piezoelectric/electrostrictive device. Then, materials constitutingpiezoelectric/electrostrictive devices of the present invention andshapes of the piezoelectric/electrostrictive devices are described. Itis preferable that a substrate, fixing plate, connection plate(connection-fixing plate), diaphragm, spring plate, spring-platereinforcement portion, and reinforcement plate are made of ceramics. Forexample, it is possible to use stabilized or partially-stabilizedzirconia, alumina, magnesia, and silicon nitride. Among thesesubstances, stabilized or partially-stabilized zirconia is mostpreferably used because it has a large mechanical strength, a hightoughness, and a small reactivity with piezoelectric films and electrodematerials.

However, when using the above stabilized or partially-stabilizedzirconia as the material of the substrate and the like, it is preferableto constitute a diaphragm by adding at least an additive such as aluminaor titania to the diaphragm.

It is not always necessary that such components constituting a substrateas a diaphragm plate, intermediate plate, base plate, fixing plate,connection plate (connection-fixing plate), spring plate, diaphragm,spring-plate reinforcement portion, and reinforcement plate are made ofthe same material. It is possible to use the above various types ofceramics for the above components by combining them in accordance withthe design. However, it is preferable to integrally constitute thecomponents by using the same material in order to secure the reliabilityof joints between portions and simplify the fabrication process.

To form a spring plate on the both planes of a connection plate, it isalso possible to use a spring plate having the same structure as apiezoelectric element for a spring plate to be formed on the plane wherepiezoelectric elements are arranged. The above case is preferable fromthe viewpoint of the fabrication process because spring plates can beformed simultaneously with piezoelectric elements. However, theelectrode of a piezoelectric element formed as a spring plate is notused as an electrode.

It is already described that the thickness and shape of a fixing plateof a piezoelectric/electrostrictive device of the present invention arenot restricted and therefore, they are properly designed in accordancewith the purpose. Moreover, the thickness of a substrate is properlydetermined by considering the operability. However, it is preferable toset the thickness of a diaphragm in a range of 3 to 20 μm and the totalthickness of a diaphragm and a piezoelectric element in a range of 15 to60 μm. Moreover, when using a spring plate, it is preferable to set thetotal thickness of a connection plate and a spring plate in a range of20 to 300 μm and the width of them in a range of 30 to 500 μm, and theaspect ratio (width/thickness) of the spring plate in a range of 0.4 to50 in any case of bonding the spring plate to either plane or bothplanes of a connection plate. Furthermore, when a spring-platereinforcement portion is necessary, it is preferable to equalize thethickness of the portion with that of a spring plate to be bonded to theportion.

Then, though piezoelectric ceramics formed like a film is preferablyused as a piezoelectric film of a piezoelectric element, it is alsopossible to use electrostrictive ceramics or ferroelectric ceramics.Moreover, it is possible to use a material requiring polarization or amaterial not requiring polarization. However, when using thepiezoelectric/electrostrictive device in this invention for a recordinghead, it is preferable to use a material having a small strainhysteresis because the linearity between the displacement amount of afixing plate and the driving or output voltage is important. Therefore,it is preferable to use a material having a coercive electric field of10 kV/mm or lower.

Specifically, as the ceramics used for the piezoelectric film, thefollowing are listed: lead zirconate, lead titanate, lead magnesiumniobate, lead nickel niobate, lead zinc niobate, lead manganese niobate,lead antimony stannate, lead manganese tungstate, lead cobalt niobate,and barium titanate or ceramics containing a component obtained bycombining some of the above materials. Among these materials, a materialmainly containing a component consisting of lead zirconate, leadtitanate, and lead magnesium niobate is preferably used for the presentinvention because the material has a high electromechanical couplingfactor and a high piezoelectric constant, and a small reactivity with asubstrate member when sintering a piezoelectric film and therefore, amaterial consisting of a predetermined composition can be stably formed.

Moreover, it is possible to use ceramics obtained by properly addingoxides of lanthanum, calcium, strontium, molybdenum, tungsten, barium,niobium, zinc, nickel, manganese, cerium, cadmium, chromium, cobalt,antimony, iron, yttrium, tantalum, lithium, bismuth or tin, orcombination of some of these materials, or other compounds to the abovepiezoelectric ceramics. Furthermore, it is preferable to control thecoercive electric field and piezoelectric characteristic of the materialwhich mainly consists of lead zirconate, lead titanate, and leadmagnesium niobate with additives such as lanthanum and strontium.

Furthermore, it is preferable that the electrode of a piezoelectricelement is constituted of metal that is solid at room temperature andthat is superior in conductivity. For example, a single metal ofaluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc,niobium, molybdenum, ruthenium, palladium, rhodium, silver, tin,tantalum, tungsten, iridium, platinum, gold, or lead, or an alloyobtained by combining some of the above metals is used for theelectrode. Moreover, it is possible to use the cermet obtained bydispersing the same material as a piezoelectric film or diaphragm in theabove metallic materials.

Actual electrode-material selection is determined depending on a methodfor forming a piezoelectric film. For example, to form a first electrodeon a diaphragm and then form a piezoelectric film on the first electrodethrough firing, it is necessary to use a high-melting-point metal suchas platinum which does not change even at a piezoelectric-film firingtemperature for the first electrode. However, because the secondelectrode formed on the piezoelectric film after the piezoelectric filmis formed can be formed at a low temperature, it is possible to use alow-melting-point metal such as aluminum.

Moreover, it is possible to form electrodes by integrally firing apiezoelectric element. In this case, however, it is necessary to use ahigh-melting-point metal withstanding the piezoelectric-film firingtemperature for both first and second electrodes. Furthermore, as shownin FIG. 3, to form the first and second electrodes 59 and 60 on apiezoelectric film 58, it is possible to form the both electrodes 59 and60 by using the same low-melting-point metal. Thus, it is possible toproperly select preferable first and second electrodes depending on apiezoelectric-film forming temperature represented by apiezoelectric-film firing temperature and a piezoelectric-elementstructure.

Then, insulating glass or resin is used as the material of an insulatingcoating layer to be formed on a piezoelectric element and an electrodelead. Here, to improve the performance of apiezoelectric/electrostrictive device so as not to interrupt adisplacement, it is preferable to use resin instead of glass as theinsulating coating material. Therefore, one of the followingfluorocarbon resins superior in chemical stability are used:tetrafluoroethylene-resin Teflon (Teflon PTF made by Du Point Inc.),tetrafluoroethylene-hexafluoropropylene copolymer-resin Teflon (TeflonFEP), tetrafluoroethylene-perfluoroalkylvinylether-copolymer-resinTeflon (Teflon PFA), and PTFE/PFA-composite Teflon. Moreover, siliconeresin (particularly, thermosetting silicone resin) is preferably usedthough it is inferior to the above fluorocarbon resins in corrosionresistance and weather resistance. Furthermore, it is possible to useepoxy resin or acrylic resin in accordance with the purpose. Moreover,it is preferable to form an insulating coating layer by using materialsdifferent from each other for a piezoelectric element and its vicinityor an electrode lead and its vicinity. Furthermore, it is alsopreferable to add inorganic and organic additives (filler) to aninsulating resin to adjust the rigidity of a diaphragm and the like.

When forming an insulating coating layer, various metals such as gold,silver, nickel, and aluminum are used as the material of a shieldinglayer formed on the insulating coating layer. Moreover, it is possibleto use every metallic material used for the electrode or the like of theabove piezoelectric elements. Furthermore, it is possible to useconductive paste obtained by mixing metallic powder with resin.

Then, a piezoelectric/electrostrictive device fabrication method of thepresent invention is described below. Slurry is manufactured by addingand mixing a binder, solvent, and dispersant to ceramic powder ofzirconia or the like serving as the material of a substrate, fixingplate, connection plate, connection-fixing plate, diaphragm, and springplate. Then, the slurry is degassed and manufacturing green sheets orgreen tapes for a diaphragm plate, intermediate plate, and base platerespectively having a predetermined thickness by the reverse roll coatermethod or doctor blade method. Unless a spring plate 18 is used, it isunnecessary to make an intermediate plate. In this case, however, tokeep the mechanical strength of a substrate, it is necessary to increasethe thickness of a base plate by that of an intermediate plate. That is,though a green sheet for intermediate-plate is not manufactured, it ispreferable to increase the thickness of a green sheet for base-plate bya value equal to the thickness of the green sheet forintermediate-plate.

Then, a through-hole 14 and a spring plate 18 are formed on a greensheet for intermediate-plate 17 as shown in FIG. 22 by using a mold orlaser beam, and a green sheet for base-plate 15 is punched into apredetermined shape so that the through-hole 14 is formed. Manufacturedgreen sheet for diaphragm-plate 3, green sheet for intermediate-plate17, and green sheet for base-plate 15 are united into one body bysuperimposing these sheets in order at least one by one and firing themto manufacture a substrate. In this case, to superimpose these greensheets 3, 15, and 17, a hole portion 8 is previously formed to determinesuperimposing positions.

It is also possible to form the through-hole 14 and the diaphragm 21 onthe green sheet for diaphragm-plate 3 in the green state. However,because the green sheet for diaphragm-plate 3 generally has a very smallthickness of 3 to 20 μm, it is preferable to obtain a predeterminedshape after forming a substrate and arranging piezoelectric elements bylaser-beam processing to be mentioned later in order to secure thesurface flatness and dimensional accuracy of the sheet 3 after sinteringa diaphragm and the like to be formed in the green sheet fordiaphragm-plate 3.

To arrange piezoelectric elements at the portion of the green sheet fordiaphragm-plate 3 on where the diaphragm 21 is finally formed, there isa method of manufacturing a substrate and a piezoelectric film at thesame time by manufacturing the piezoelectric film in accordance with thepress molding method using a mold or the tape forming method usingslurry and thereby superimposing the green piezoelectric film at theposition of the green sheet for diaphragm-plate 3 on where the diaphragmis formed under applying a heat and a pressure, and then co-firing thepiezoelectric film and substrate. In this case, however, it is necessaryto previously form an electrode on the substrate or piezoelectric filmby using a film forming method to be described later.

Though the temperature for firing a piezoelectric film is properlydetermined depending on the material constituting the piezoelectricfilm, it is generally set to 800° to 1,400° C., preferably set to 1,000°to 1,400° C. In this case, it is preferable to sinter the piezoelectricfilm under the existence of the evaporation source of the material ofthe piezoelectric film in order to control the composition of thepiezoelectric film. Moreover, to sinter the piezoelectric film and thesubstrate at the same time, it is naturally necessary to match thefiring conditions of both to each other.

When using the film forming method, it is possible to arrangepiezoelectric elements at the position of diaphragm forming on asintered substrate through one of a thick-film forming method such asthe screen printing method, dipping method, and coating method and oneof various thin-film forming methods such as the ion beam method,sputtering method, vacuum deposition, ion plating method, chemical vapordeposition method (CVD), and plating. Among these methods, in the caseof the present invention, a thick-film forming method according to oneof the screen printing method, dipping method, and coating method ispreferably used to form a piezoelectric film. These methods make itpossible to form a piezoelectric film by using paste or slurry mainlycontaining piezoelectric ceramic particles having an average particlesize of 0.01 to 5 μm, preferably 0.05 to 3 μm and thus, a preferablepiezoelectric operation characteristic is obtained.

For example, after sintering a manufactured substrate under apredetermined condition, a first electrode is printed at a predeterminedposition on the surface of a diaphragm plate and fired, then apiezoelectric film is printed and fired, and moreover a second electrodeis printed and fired to arrange piezoelectric elements. Then, anelectrode lead for connecting each formed electrode to a measuringinstrument is printed and fired. In this case, when using platinum (Pt)as the first electrode, lead zirconate titanate (PZT) as thepiezoelectric films, gold (Au) as the second electrode, and silver (Ag)as the electrode lead, at a certain sintering stage, a material sinteredbefore the sintering stage is not re-sintered because the firingtemperature in the firing process is set so as to successively lower.Thus, it is possible to prevent a trouble such as separation or cohesionof an electrode material or the like from occurring.

By selecting a proper material, it is possible to sinter each member ofa piezoelectric element and electrode leads integrally at one timethrough successively printing them, and it is also possible to form eachelectrode at a low temperature after forming a piezoelectric film.Moreover, it is possible to form each member of a piezoelectric elementand electrode leads through a thin film method such as the sputteringmethod or vacuum deposition method. In this case, heat treatment is notalways necessary.

Thus, by forming a piezoelectric element through a film forming method,it is possible to integrally bond and arrange a piezoelectric elementand a diaphragm without using any adhesive, to secure reliability andreproductibity, and simply integration. Moreover, in this case, it ispossible to form a piezoelectric film into a proper pattern. As theforming method, it is possible to use the screen printing method,photolithography method, laser-beam processing method, or machiningmethod such as slicing or ultrasonic processing.

Then, a diaphragm and a fixing plate are formed at a predeterminedposition on a manufactured substrate. In this case, it is preferable tocut out and remove the green sheet for diaphragm-plate 3 through themachining using the fourth harmonic wave of a YAG laser. Thus, it ispossible to form the through-hole 14 while leaving the portionsintegrally joined to a substrate such as a fixing plate and a diaphragmshown in FIGS. 18(a) to 18(d). In this case, it is possible to adjust adisplacement amount by adjusting the shapes of the fixing plate anddiaphragm.

Moreover, as shown in FIG. 23, it is possible to obtain a predetermineddisplacement characteristic by using the first electrode 22 as an upperelectrode and the second electrode 24 as a lower electrode and therebyonce setting the piezoelectric element 25 on which the piezoelectricfilm 23 is formed between the upper and lower electrodes, thereafterremoving the upper electrode through the fourth harmonic wave of YAGlaser or machining, and adjusting the effective electrode area of thepiezoelectric element and moreover adjusting the electricalcharacteristics including impedance of a piezoelectric/electrostrictivedevice. When the structure of the piezoelectric element 25 is the combstructure shown in FIG. 3 or 4, it is necessary to remove a part ofeither electrode or parts of both electrodes.

For the above machining, it is possible to use one of various machiningmethods suitable for the size and shape of a resonant portion such aslaser-beam processing using a YAG laser, second or third harmonic waveof the YAG laser, excimer laser, or CO₂ laser, electron beam processing,and dicing (machining) in addition to the above machining using thefourth harmonic wave of the YAG laser.

Moreover, it is possible to fabricate a piezoelectric/electrostrictivedevice of the present invention by using the pressure molding methodusing a forming die or slip casting method, or injection molding methodin addition to the fabrication method using the above green sheets. Alsoin these cases, a piezoelectric/electrostrictive device of the presentinvention is machined through machining such as cutting or grindingbefore and after firing, punching through laser-beam processing orpressing, or ultrasonic processing and formed into a predeterminedshape.

It is possible to form an insulating coating layer to be formed over apiezoelectric element and an electrode lead of thepiezoelectric/electrostrictive device thus fabricated by using glass orresin through the screen printing method, coating method, or sprayingmethod. In this case, when using glass as a material, it is necessary toraise the piezoelectric/electrostrictive device up to approximately thesoftening temperature of glass. Moreover, because glass has a largehardness, it may interrupt displacement or oscillation. However, becauseresin is soft and only requires treatment such as drying, it ispreferable to use resin. It is already described that fluorocarbon resinor silicone resin is preferably used as the resin for forming aninsulating coating layer. When using one of these resins, however, it ispreferable to form a primer layer corresponding to the resin used andthe type of ceramics and form an insulating coating layer on the primerlayer in order to improve the adhesion of the resin with base ceramics.

Then, in the case of formation of a shielding layer formed on aninsulating coating layer, it is difficult to perform firing when theinsulating coating layer is made of resin. Therefore, when using variousmetallic materials, the shield layer is formed by a method requiring noheat such as the sputtering method. However, when using conductive pastemade of metallic powder and resin, it is possible to properly use thescreen printing method and coating method. When forming the insulatingcoating layer with glass, it is also possible to screen-printing andfiring metallic paste at a temperature at which the glass does not flowor lower.

The configuration, materials, and fabrication method of apiezoelectric/electrostrictive device of the present invention aredescribed above in detail. However, it is needless to say that thepresent invention is not restricted to the above embodiments. It shouldbe understood that the present invention can be modified, corrected, orimproved in accordance with the knowledge of a person skilled in the artas long as a modified, corrected, or improved embodiment does notdeviate from the gist of the present invention.

Industrial Applicability

A piezoelectric/electrostrictive device of the present invention ischaracterized in that the structure is simple and thus, the device iseasily reduced in size and weight and hardly influenced by externalharmful vibrations, and allows both static and dynamic displacements tobe accurately controlled by using a piezoelectric element. Moreover, thedevice has an advantage that it can be inexpensively fabricated by asimple fabrication method. Furthermore, the device has an advantage thata proper material can be used each time in accordance with the purposebecause component materials can be selected in a wide range. Therefore,when the device is set in various actuators and sensors, high-accuracycontrol and measurement are realized and moreover, a superior advantageis obtained that the device contributes to reduction in size and weightof the actuators and sensors.

What is claimed is:
 1. A piezoelectric/electrostrictive devicecomprising: a substrate; a connection plate having a first end and asecond end opposed thereto along a first direction, and a first side anda second side opposed thereto along a second direction perpendicular tosaid first direction, said first end being joined to said substrate; afixing plate joined to said second end of said connection plate; a firstdiaphragm having a first side joined to said first side of saidconnection plate and a second side opposed to said first side along saidsecond direction, said second side of said first diaphragm being joinedto said substrate; a second diaphragm having a first side joined to saidsubstrate and a second side opposed thereto in said second direction,said second side of said second diaphragm being joined to said secondside of said connection plate; and a piezoelectric/electrostrictiveelement provided on at least a portion of at least one planar surface ofat least one of said diaphragms.
 2. The piezoelectric/electrostrictivedevice according to claim 1, wherein the piezoelectric/electrostrictiveelement is provided on one of said diaphragms and at least one slit isformed on the other one of said diaphragms.
 3. Thepiezoelectric/electrostrictive device according to claim 1 , wherein aslit or constricted portion is formed on the connection plate.
 4. Thepiezoelectric/electrostrictive device according to claim 1, wherein thefixing plate, the connection plate, and the diaphragms are integrallyformed from one diaphragm sheet, and the substrate is formed bylaminating integrally said diaphragm sheet and a base sheet.
 5. Thepiezoelectric/electrostrictive device according to claim 1, wherein aspring plate is bonded to at least one plane of the connection plate andjoined to the substrate or a spring-plate reinforcement portion formedon the substrate.
 6. The piezoelectric/electrostrictive device accordingto claim 5, wherein the spring plate is either formed integrally from anintermediate sheet interposed between and integrated with a diaphragmsheet and a base sheet for the substrate, or formed integrally with aspring-plate reinforcement portion formed integrally with a diaphragmsheet, and formed integrally with the connection plate.
 7. Thepiezoelectric/electrostrictive device according to claim 5, wherein thesubstrate, the fixing plate, the connection plate, the diaphragm, aspring plate, and a spring-plate reinforcement portion are made ofstabilized zirconia or partially-stabilized zirconia.
 8. Thepiezoelectric/electrostrictive device according to claim 5, wherein theshape of at least one of the fixing plate, the connection plate, thediaphragm, and a spring plate is dimension-adjusted by trimming itthrough laser-beam machining or cutting.
 9. Thepiezoelectric/electrostrictive device according to claim 1, wherein byusing as a center axis a vertical axis passing vertically through thecenter of a fixed plane which is a connection surface between the fixingplate and the diaphragm, the piezoelectric/electrostrictive deviceoperates in accordance with at least either of a θ-mode displacement inwhich the fixing plate displaces like a pendulum in a direction verticalto a side of the fixing plate and vertical to the vertical axis or aφ-mode displacement in which a swing in a direction vertical to a sideof the diaphragm and vertical to the vertical axis centering around thevertical axis displaces like a pendulum while being followed by a swingin a direction parallel with the side of the fixing plate.
 10. Thepiezoelectric/electrostrictive device according to claim 1, wherein atleast a portion of the diaphragms and at least a portion of theconnection plate are joined to the side of a through-hole formed in thesubstrate.
 11. The piezoelectric/electrostrictive device according toclaim 1, wherein at least two piezoelectric/electrostrictive elementsare provided at different locations on at least one of the diaphragms,at least one of the piezoelectric/electrostrictive elements is used as adriving element and at least one of the remainingpiezoelectric/electrostrictive elements is used as an assistant elementfor driving the piezoelectric/electrostrictive device.
 12. Thepiezoelectric/electrostrictive device according to claim 1, wherein thepiezoelectric/electrostrictive element and a lead used for joiningelectrically to an electrode of the piezoelectric/electrostrictiveelement are covered with an insulating coating layer made of a resin ora glass.
 13. The piezoelectric/electrostrictive device according toclaim 12, wherein the resin is a fluorocarbon resin or a silicone resin.14. The piezoelectric/electrostrictive device according to claim 12,wherein a shielding layer made of a conductive material is furtherformed on the surface of the insulating coating layer.
 15. Thepiezoelectric/electrostrictive device according to claim 1, wherein apiezoelectric material forming the piezoelectric/electrostrictiveelement is made of a material mainly containing a component consistingof lead zirconate, lead titanate, and lead magnesium niobate.
 16. Thepiezoelectric/electrostrictive device according to claim 1, wherein theelectrode of the piezoelectric/electrostrictive element islaser-beam-machined or cut and thereby, the effective electrode area ofthe piezoelectric/electrostrictive element is adjusted.
 17. Thepiezoelectric/electrostrictive device according to claim 1, wherein eachof said first and second diaphragms has a third side joined to saidsubstrate.